When penetrations must be sealed for air infiltration purposes, there are several options available. A good grade of silicone, acrylic, or siliconized acrylic caulking (DO NOT use oil-base caulks), most of the canned expanding foams, and open- or closed-cell pipe insulation are good sealing materials and may be used in direct contact with PEX tubing. .... There are a number of fire stopping compounds readily available that have been listed for use with PEX tubing. These compounds come in standard caulking tubes and are identified as waterbased, acrylic or latex
. Consult the compound manufacturers’ instructions for proper application.